Process and apparatus for treating oil



Dec. 5, 1939. H. c. EDDY PROCESS AND APPARATUS FOR TREATING OIL FiledJan. 26, 1937- `l?, Sheets-Sheet l /NvE/vroR HAROLD C. EDDY HARRIS,KlEC/-ll FOSTER@ HARRIS Fwd AT TOR/vim.

Dec. 5, 1939. H. c, EDDY 2,182,145

` PRocEss AND APPARATUS FOR TREATING OIL Filed Jan. 26, 1957 2Sheets-Sheet 2 mmwmz f /h/vvE/vrof'? 95 H ARoLD C. EDDY Y v HA RR/S,K/fcH, F05 TERa HA RR/ A T TOR/VE yq.

Patented Dec. 5, 1939 UNITED STATES I l 2,182,145 raocass Ann APPARTUSFon.' 'rnEA'rrNG Harold C. Eddy, Los Angeles, Calif., assigner, by mesneassignments, to Petrolite Corporation, Ltd., Wilmington, Del., acorporation of Dela- Ware Application January 26, 1937, Serial No.122,470

20 Claims.

oils may be substantially dry, or may contain a small proportion ofwater dispersed therein, the

percentage of water being very small and never exceeding more than a fewper cent.

By way of example, the invention is well adapted to treatment ofpetroleum oils or other hydrocarbons preparatory to refining or crackingin subsequent refining steps. It is in this capacity of treatingpetroleum oils that the invention will be particularly described, thoughthe same principles can be applied to the treating of other oils.

In modern refinery practice, it has been found that the oil reaching therefinery as a refinery charging stock contains various impurities. Thewater content thereof is usually low, seldom exceeding more than a fewper cent. This water, if present, will be in the form of minute dropletsdispersed in the oil and various impurities may be dissolved therein,for instance acids or various salts or both. Such salts may be calciumchloride, magnesium chloride, sodium chloride, etc. In addition, thisoil may contain various other impurities dissolved in, or dispersed inthe oil itself, as distinct from the water. For instance, this oil maycontain acids or other impurities present in the oil itself. Such acidsor other impurities may simultaneously exist in the oil and in thedispersed water droplets, if present.

It is an object of the present invention to remove impurities from oilspreparatory to passage through subsequent refining equipment, theseimpurities being of such character that they will deleteriously affectthe refining equipment, as by corroding the metal portions thereof orcausing depositions thereon, and may deleteriously affect the finishedproduct or products. f

For example, the deleterious reactions resulting from the presence ofacids in the oil are well known. In addition, it has now beenascertained that certain salts present in the incoming oil will reactunder high temperature to form acids.

For instance, salts such as calcium chloride or magnesium chloride willreact with water when at a temperature of approximately 250 F or oaboveto form hydrochloric acid. Such acids are very corrosive. Reflneriesfaced with this problem have found it necessary to neutralize the effectof the acids by addition of ammonia, a procedure involving considerableexpense. In addition, salts in the incoming oil are themselves depositedon tube walls, thus clogging the passages, for example renderingineffective the desired heat transfer in the heat exchangers. Also, suchsalts appear to act as catalyzing agents tending to fuse coke to theheated tubes of the subsequent refinery equipment. Use of the presentinvention has made possible removal of a major portion of suchimpurities, thus increasing the life of the refinery equipment, verymaterially increasing the length of time that the equipment can beoperated without cleaning, and resulting in the production of superiorproducts, often with considerably increased yields. Relative to thislast factor, a 6% increase in yield has sometimes been made in using theinvention. In addition, if the invention is used in conjunction with arefining system producing asphalt, the asphalt will be of extremelyhighsolubility, meeting very exacting requirements often impossible to meetif the rening equipment isused on oil not subjected to treatment inaccordance with the present invention.

Crude oil produced by most wells is in the form of anemulslon,containing from 10% to 80% water, usually in the form of brine. Variousmethods have been proposed for reducing this water content preparatoryto distillation. Dehydration methods involving gravitational separation,chemical treatment, centrifugal treatment, application of heat,filtration, or use of an electric field have been proposed. If all ofthe water could thus be removed, the water-dissolved salts wouldlikewise be taken out. However, no dehydration method has been foundwhich will commercially accomplish such complete removal. Even with thebest commercial dehydration methods/available, the resulting oil mayoften contain several hundred grams of salt per barrel, even if thewater content has beenreduced to below .5%. For instance, subjection ofmany such crude oils to an electric field will cause coalescence of thewater masses and produce an oil having a water content which is oftenbelow 1%. v Even then, however, the salt content of this water may be sohigh as to seriously affect subsequent renlng equipment. Even ifsuccessive dehydrating actions are utilized on the same oil, it will befound impossible to remove all of the water. Many of the oils presentingthe greatest problems are those containing onlyv a small fraction of 1%of Wateroils which have been treated by the best known methods in anattempt to remove substantially-all of the water.

'I'he present purification process can be advantageously used on suchpreviously dehydrated 5 oils, topped oils or other oils of low watercontent, and will remove a major portion of the impurities, for instancethe salts, acids or other impurities dissolved in the water, or theacids or other impurities associated with the oil itself. The presentpurification process should thus not be confused with the usualdehydration processes. It can well start where other crude oil dehy-'lrating processes end, and may receive a dehydrated oil ofvery lowwater content and on which the electrical dehydrating process as atpresent practised has no material dehydrating effect.

It will be clear, however, that the invention is not limited byprocesses to which the oil has pre- 2o viously been subjected beforereaching the reiinery. It will particularly be described as purifyingoil containing not more than a few per cent of water and such oil may bean oil which has been previously dehydrated byany known process, or anoil naturally containing this low percentage of water, or an oilresulting from mixing or blending oils of greater water content withoils of lower water content. In other instances, the

water may be the result of previously-performed steps, whether or notthey are of a dehydrating character. The oils to which this invention isparticularly applicable are those oils which have a very low watercontent, never more than a few per cent and usually less than two percent,

though this water content may often be materially below one-half of oneper cent. The 1nvention is also applicable to the removal ofoilassociated impurities regardless of whether dispersed water dropletsare present.

When treating an oil containing dispersed water droplets, it is anobject of the present invention to add a controlled amount of water, andto control the mixing action to produce a resulting mixture in which amajor portion of the original water droplets coexist with droplets ofthe added water. This mixture is then subJected to the action of anelectric field where coalescence of the coexisting droplets takes place.It will thus be clear that it is not the intention of the presentprocess to use such violent mixing as would cause the added water tobecome combined with the original water during the mixing step. Theinvention thus and in other ways departs from previous proposals, and ithas been found that very emcient removal of impurities can be obtainedby first forming a mixture containing coexisting droplets of theoriginal and added water, and then electrically coalescing thesedroplets as. distinct from attempting to combine them during the mixingstep.

Best results have been obtained on most oils if such mixing is used asto form a relatively loose emulsion or mixture. For instance, thisrelatively loose emulsion or mixture may desirably be of such acharacter that a major portion of the added water will gravitationallyseparate, partly as emulsion and partly as free water, if

the newly formed emulsion is allowed to stand.

quiescent for two or three days, at the existing elevated temperature.

mixing can be of such a character that about 90% of the water will thusseparate.' It will be found, however, that this separated water will notcontain any large portion of the salts or other waterdissolvedimpurities which are to be removed.

In some instances, the- However, if the mixture with its coexistingdroplets is subjected to the action of an electric eld, it will be foundthat the droplets of the added water coalesce in large measure with thedroplets of the original water under the action of the electric stress.When the coalesced masses are permitted to gravitationally separate, itwill be found that a major portion of the water-dissolved impuritiespresent in the incoming oil will now be associated with the settledwater.

During this gravitational separation, the treated oil will rise. Whenanalyzed, it will usually be found to contain minute droplets of water,predominantly droplets of the added water as distinct from droplets ofthe original water. Its salt content; will be only a small fraction ofthe salt content of the incoming oil. In some instances, more than 90%of the water-dissolved impurities are removed by the process. Theprocess is fundamentally not a dehydration process. For instance, if theincoming oil contains 1% of brine dispersed in minute droplets of a sizeapproximating one mu, the treated oil will usually contain. about thesame amount of water, sometimes slightly more and sometimes slightlyless, but the water will predominantly be in the form of minute dropletsof the added water. The particle size may still be in the neighborhoodof one mu. Thel net eii'ect of the process is thus to replace in largemeasure the droplets of original water in the oil with droplets o f theadded water.

The added water can usually be taken from available sources. It need notbe distilled water, and various so-called fresh waters can be used. Theadded Water may carry certain salts in low concentration, though it isessential that the added water should be relatively fresh so as not tocontain the same salts in the same concentration as present in theoriginal water droplets. Stated in other words, the added water must beof different composition from the water droplets present in the incomingoil, by which term I have reference to a difference in chemicalcomposition or a difference in concentration, or both. Differentlystated but of the same meaning, the added water should be substantiallymore free of the impurities to be removed than is the water forming theoriginal water droplets with which the impurities are associated. Itwill be clear that, if the added water contains the same salts as arepresent in the original water droplets, but in lower concentration, thenet salt content will be reduced by the process because of thereplacement ofthe original water droplets by the added water droplets.On the other hand, the chemical composition of the added water may bedifferent from that of the original water droplets, even though theconcentration is higher. In this instance, replacement of the originalwater droplets by the added water droplets may give an oil in which thetotal salt content, expressed in grams per barrel, may be higher thanthat of the incoming oil, but the process may still be of utility inthat the chemicals in the added water will not deleteriously affect thesubsequent process, equipment or the products produced. Usually,however, the chemical composition of the added water is 'different fromthat of the original water droplets, and the concentration of thechemicals therein, if any, is considerably lower than the concentrationof the original brine droplets.

In many instances, it has been found desirable to successively emulsifythe oil and the added water so that no single emulsifying action need beexcessively large. It has often been found desirable to perform the lastemulsifying step immediately prior to introduction into an electricfield, for instance by using an emulsifying means for dischargingdirectly into the field, though this direct introduction is notinvariably necessary, particularly on heavy oils.

From the standpoint of removing impurities dissolved in, or dispersedin, the oil, the present invention produces quite unexpected results.Assuming a substantially dry oil with acid dissolved therein, it hasbeen found possible to add water and mix to form a relatively looseemulsion. If this added water is settled out, or other- Wise removedbefore subjection to an electric eld, it will be found that very littleof the acid has entered the water. However, if the mixture is formed inaccordance with the present invention and is subjected to the action ofan electric field to coalesce the droplets of added Water, it will befound that these coalesced masses contain a major portion of the acid.Just why this is the case is not completely understood, though my testsdefinitely show that the electric field has some action tending totransfer the oil-dissolved acids or other impurities to the water. Soalso materials dispersed in the oil, for instance solid matter such asmud or sand, are similarly removed, but here again the process does notcause these materials to become largely associated with the water in themixing step. The action of the electric field is relied upon in thisregard.

In thus removing impurities dissolved in the oil, or molecularly orcolloidally dispersed there-` in, it is not essential that the oil besubstantially dry. Removal of such impurities is not defeated by thepresence of water droplets, though the process 4is best adapted to oilscontaining not more than a few per cent of water. In some instances,such dispersed water droplets may carry certain salts, or even a portionof the acid, dis# solved therein. In such instance, the process willreplace most of the original water droplets with droplets of the addedwater, and will also remove the impurities associated with the oilitself.

It is an object of the present invention toprovide a novel method andapparatus involving the use of one or more of the above concepts in theremoval of impurities from an oil.

Various other objects and advantages will be evident to those skilled inthe art from the following description of a selected embodiment of theinvention. For purpose of-illustration, this embodiment will bedescribed with reference to processing a petroleum oil preparatory tosubjection to cracking temperatures in a refining installation.

Referring to the drawings:

Fig 1 is a pipe-line diagram of a refining system, very diagrammaticallyshown, and indicates one arrangement of the invention in conjunctiontherewith.

Fig. 2 is a sectional view of one type of emulsifying valve.

Fig. 3 is a vertical sectional view of the preferred form of electrictreater diagrammatically illustrated in Fig. 1.

Fig. 4 is an enlarged fragmentary view of the upper and intermediateelectrode structure.

Fig. 5 is a sectional view of the emulsifying valve discharging into theelectric field.

Fig. 6 is a sectionalvview of the washing device of the invention.

In Fig. 1 I have very diagrammatically shown one type of refining systemI0 comprising a fractionating means for removing various fractions ,II,I2, I3, and I4 are shown.

The refining unit Il is shown as including a still 2I, a tower 22, aheat exchanger 23, and a condenser 24. No attempt has been made to showreflux systems or specific details of these structures, such featuresbeing well known. in the art. Sufce it to say that the incoming oil tobe refined is heated in the still 2| by any suitable heating means, thevapors moving through a pipe 25 to the tower 22. Vapors are dischargedfrom this tower through a pipe 26 which communicates with one of twopassages formed by the heat exchanger 23, vthese passages being inheattransferring relationship with each other. The vapors are somewhatcooled in the heat exchanger 23, being partially condensed therein, thedischarge of this one passage communicating with a pipe 21 whichconducts the vapors, and any condensate formed, to a pipe means in thecondenser 24. Cool Water is circulated through this condenser, beingintroduced through a pipe 28 and Withdrawn through a pipe 29, flowingthrough a passage means which is in heat-transferring relationship withthe vapors. These vapors are thus condensed, and the condensate isdischarged through a pipe 30.

Similarly, the refining unit I2 includes a still 3|, a tower 32, a heatexchanger 33, and va condenser 34. The vapors move to the tower 32through a pipe 35 and to the heat exchanger 33 through a pipe 36, movingto the condenser 34 through a pipe 31. The cooling water enters thiscondenser through a pipe 38 and is discharged through a pipe 39, thecondensate being discharged through a pipe 40.

'I'he refining unit I3 is similarly constructed with a still 4I, a tower42, a heat exchanger 43, and a condenser 44 to which the vapors arerespectively delivered by pipes 45, 46, and 41. The Water enters thecondenser 44 through the pipe 43 and is discharged through a pipe 49,the condensate being discharged through a pipe 50.

Relative to the refining unit I4, this unit includes a still 5I, a tower52, a heat exchanger 53, and a condenser 54, to which vapors aredelivered through pipes 55, 56, and 51. Water enters the condenser 54through the pipe 58 and is discharged through the pipe 59, thecondensate being discharged through a pipe 60.

These rening units are only diagrammatically shown and can beconsiderably varied in design without departing from the spirit of theinvention. Thus, in many instances the stills and towers are combined,or various structures other than shown are utilized. However, in therening units shown, as well as in other systems, the heat exchanger andthe condenser form a heat-exchange means, and it is usually desirable topreliminarily heat the incoming dehydrated oil by use of such aheat-exchange means.

In the system shown the crude oil from the well is pumped through a pipe65 to a suitable dehydrator 66 which separates a major part of the watercontent, the water being discharged through a pipe 61. This dehydratormay be of any suitable type, relying upon electrical, centrifugal, orchemical action, or upon the action of heat, or it may comprise merely asettling means. The function of this dehydrator is to produce adehydrated oil having a low water content. 'I'his dehydrated oil ispumped from the pipe line with or without intermediate storage means maybe utilized to connect the dehydrator to the tank 10. It will also beclear that any other method of forming or processing the oil to betreated may be used: In the subsequent description of the apparatus itwill be assumed that this oil contains about 1% of water in which4various impurities are dissolved, and that the oil itself contains aciddissolved therein.

This oil is pumped from the tank 10 by a pump 1| and moves through a,pipe 12 to one of the passages of the heat exchanger 23. Thereafter itmoves through a pipe 13 through the heat exchanger 33 and dischargesinto a pipe 15 in heated condition.

In the system shown a stream of hot water is introduced-at right anglesinto the owing stream of dehydrated oil in the pipe 15 through a pipe16, the flow being controlled by a valve 11. A preliminary mixture isformed when these liquids are brought into contact, and this mixingaction may be the first of several used to form the resulting,relatively loose emulsion or mixture. This preliminary mixture .flowsthrough a pipe 18 where further mixing may take place due to turbulentow.

While various sources of water may be utilized, as above mentioned, thesystem shown in Fig. 1 utilizes the cooling water of the condenser 34 inthis capacity. This water is heated during passage through thiscondenser and is delivered bythe pipe 39 to an auxiliary heater 19 whereadditional heat may be supplied thereto fo-r control purposes. Varioustypes of heaters may be utilized, but I have found it very satisfactoryto use exhaust steam for further heating water in the heater'19. Thissteam may be introduced through a pipe 80 connected to a suitable coil,the condensate being discharged through a pipe 8|. On the other hand,the steam may be introduced directly intov the Water if desired.

The heated water moves from the auxiliary heater 19 through apipe 82 toa pump 83 which develops s'uflicient pressure to force this hot wa` terthrough the pipe 16 and into the flowing stream of dehydrated oil in thepipe 15.

Various means may be utilized for further mixing or emulsifying thepreliminary mixture moving through the pipe 18. An emulsiiler isindicated by the numeral 85 as receiving this preliminary mixture anddischarging same in emulsied condition into a pipe 86 leading to theelectric treater 81. Such an emulsiiier may comprise any properlydesigned 'emulsifying device which forms an emulsion of the desiredcharacter by mechanical mixing, friction, centrifugal force, etc. Onetype of emulsiiler which I have found to be very simple and eiective isillustrated in Fig. 2 and comprises a weighted valve 88, a stem 89 ofwhich is moved downward by a linkage including an arm 90 on which isadjustably positioned a weight 9|. The position of this weight on thearm 90 controls the pressure diilerential on opposite sides of the valveand controls the size of a passage 92 between a seat 93 and a valvemember 94. It thus controls the emulsifying tendency.

As an auxiliary emulsiiier I have disclosed a pump 95 capable ofwithdrawing the preliminarily mixed liquid from the pipe 18 through apipe 96 as controlled by a valve 91. This pump may be of any typeserving to form the desired type of mixture, for instance, a properlydesigned and properly controlled centrifugal pump capable of forming thedesired type of mixture without in itself causing a major portion of theoriginal water droplets to coalesce with the added water during thepump-induced mixing action. The discharge of the pump 95 may be returnedthrough a pipe 98 as controlled by a valve 99 to the pipe 18 ahead ofthe emulsier 85'. In this instance further mixing will take place in theemulsifler 85.y However, if this further mixing is not desired, the pump95 may discharge into the pipe 86 through a pipe |00, the ow beingcontrolled by a valve 0|. In some instances the pump 95 can be utilizedfor emulsifying purposes exclusive of the emulsier 85, in which event avalve |02`in the pipe 86 is closed. However, in most oils a pump-inducedmixing action is not as desirable as the other mixing actions described.In other instances the emulsier 85 can be used to the exclusion of thepump 95 by opening the valve |02 and closing the valves 91, 99, and |0|.In other instances these emulsifying means may be used in conjunctionwith each other by closing a valve |83 in the pipe 18, the valves 91,99, and |02 being open, the

valve 0| being closed.

In some instances the system will .work particularly well if the mixtureowing through the pipe 18 is divided into two streams, one flowingthrough the emulsiiier 85 and the other flowing through the pipes 98 and|00 to by-pass the emulsiiier, joining with the stream delivered fromthis emulsifier at a point therebeyond. For instance, the valves 99 and|0I may be adjusted to control the amount of mixture which by-passes theemulsier. That portion of the stream which moves through the emulsifierwill be more intimately mixed, and the by-passed stream will mixtherewith when injected thereinto. The size of the added water dropletsin the resulting mixture can thus be varied, for the droplets in thebypassed stream may be of an average size larger than those in thestream moving through lthe emulsiiier 85.

It is often desirable to mix the dehydrated oil and the added water insteps rather than completely mixing in a single device. This permits agradual formation of the mixture which appears to be desirable in manyinstances, as distinct from a single and more violent mixing action. Theemulsifier 85 and the pump 95 may serve to successively emulsify, as canalso the pipes 18 and 86 if they are of small enough diameter to causeconsiderable turbulence and consequent mixing therein. In addition, ithas-been found that in some instances better results can be obtained byfurther mixing immediately prior to injection into the electric eld. Forthis purpose the pipe 86 may be connected to an emulsifying distributormeans |05 disposed in the electric treater 81 and best shown in Figs. 3and 5.

Referring to Fig. 5, it will be noted that the pipe 86 carries aprimarymember |06 which cooperates with a secondary member |01 informing an annular discharge passage |08. Further mixing takes place asthe liquids move through this annular discharge passage. It is oftenpossible to movably mount the secondary member |01, resiliently movingit toward the primary member |06 so that the size of the annulardischarge passage |08 is dependent upon the quantity of the mixturemoving through the pipe 86. In accomplishing this result the secondarymember |01 may be provided with a pin |08a guided in a spider |09 andcarrying a spacer l0 at its lower end. A compression spring is disposedbetween the spider |09 and the spacer ||0 and serves to resiliently movethe secondary member |01 downward. When no liquid is moving through thepipe 86, the members |06 and |01 will be in contact, but as soon as aflow is established the pressure will force the secondary member |01upward a slight distance to open the annular discharge passage |08 indegree proportional `to the quantity of liquid'to be discharged.

'Ihe details of one type of treater 01 which I have found particularlyadvantageous in the process are best shown in Fig. 3. Referring tov thisfigure, this treater 81 provides a tank ||5 including a top member ||6and abottom member ||1, this tank being grounded as indicated by thenumeral H8.

Suspended from insulators ||9 is a live electrode means shown asincluding an upper live electrode |20 and a lower live electrode |2|,the latter being supported from and electrically connected to the upperlive electrode |20 by rods |22.

Suspended from an insulator |24 and positioned between the upper andlower live electrodes |20 and |2| is an intermediate live electrodestructure |25 respectively cooperating with the electrodes |20 and |2|in providing an upper treating space |26 and a lower treating space |21.I prefer to form the intermediate electrode structure |25 of twoelectrodes |28 and |29 connected by a support |30.

'I'he electrodes |20, |2|, |26, and |29 are preferably formed ofinterstitial character. A form of construction which I have foundparticularly desirable is illustrated in Figs. 3 and 4. Referring to theelectrode |20, this electrode is shown as including a plurality of innerand outer rings |32 and |33 between. which extend rods or pipes |34.Pins |36 depend therefrom and carry a plurality of concentric rings |31each of which provides a lower edge |38 adjacent which the electricfield is very concentrated.

The electrode |28 is similarly formed with rods or pipes |40 extendingoutward from a support |4| and carrying upward-extending pins which inturn mount a plurality of concentric rings |43. The rings |43 arepreferably disaligned from the rings |31 so that the most intenseportion of any electric field established in the treating space |26-isinclined as indicated by dotted lines |44 in Fig. 4. Such anedge-to-edge field is very effective.

The electrode |29 is formed similar to the electrode |20 and providesdownward-extending rings |50. Similarly, the electrode |2| is formedsimilar to the electrode |28'and provides upwardextending rings |5| sothat a field is established in the treating space |21 similar to thatpreviously described in the treating space |26. I have found itpreferable to form the electrodes |2| and |23 of smaller diameter thanthe electrodes |20 and |20.

This type of electrode structure presents a minimum impedance togravitational separation in the tank ||5, the rings and the supportingmeans therefor covering only a small fraction of the totalcross-sectional area of the tank. Further, the interstitial nature ofthese electrodes permits free communication between the electric fieldsand facilitates rapid removal of coalesced wate'r masses therefrom.

Various means may be utilized for energizing the electrodes to establishelectric fields in the treating spaces |26 `and |21. In the constructionillustrated all of these electrodes are live,

relation.

the only grounded portions being the tank and the emulsifyingdistributor means |05, the latter discharging directly into the treatingspace |21 to move the emulsion outward therein and successively throughthe edge-to-edge fields. By proper design of the electrical system, thepo-A tential between the intermediate electrode structure |25 and theelectrodes |20 vor |2| can be made much higher than the potentialbetween any of the live electrodes and ground. In Fig. 3 such a systemis shown as including two transformers |60 and |6| connected in additiveIn this connection one terminal of each secondary winding is grounded asindicated by the numeral |62, the high tension terminal of thetransformer |6| being connected by a conductor |63 to the intermediateelectrode structure |25, and the high tension terminal of thetransformer |60 is connected by a conductor |64 to the upper and lowerlive electrodes |20 and |2|. Suitable switches and control meanslimiting the current to the primaries of these transformers may beutilized, such means being well known in the art of electric dehydrationof emulsions.

Assuming, for instance, that each transformer develops a potential of12,000 volts, the potential across the upper treating space |26 will be24,000 volts, as will also the potential across the lower treating space|21. However, the potential between the emulsifying distributor means|05 and the electrode |29, or the electrode |2|, will be only 12,000volts.A Use of such a system tends to prevent short-circuiting to theemulsifying distributor means |05 and also permits introduction of theresulting mixture directly into a eld of vhigh voltage. I believe it tobe new to utilize upper and lower live electrodes with an intermediatelive electrode in this capacity, though various other electrode systemscan be utilized without departing from the spirit of the presentinvention as applied to the removal of foreign matter from oils.

The action of the electric fields is to bring into contact and thuscoalesce in large measure the co-existing original and added waterparticles of the newly formed mixture into masses of sufflcient size togravitate from the oil. Thus, after the treater has been in operationfor a period, the upper end of the tank ||5 will contain the treated oiland the lower end of the tank will contain a body of separated water.These bodies will separate at a rather definite surface or levelindicated in Fig. 3 by the numeral |10. It is desirable to ratherdenitely control this level to prevent grounding of the electrode |2|.In this connection, it will be apparent that an electric field will beestablished in an auxiliary treating space |1| between the lower liveelectrode |2|`and the body of water in the bottom of the tank ||5. Ifthe level |10 is carried 'too high, this auxiliary eld may short out.However, with proper control of the level |10, this auxiliary field canbe utilized to further treat the settling water particles and can beused to break an inverse-phase or reverse-phase'emulsion, as will behereinafter ldescribed.

To control the water level in the tank ||5, I have shown an automaticsystem including a pipe |15 communicating with the upper part of thetank ||5 and a pipe |16 communicating with a water draw-oil pipe |11which opens on the lower end of the tank H5. I'he pipes |15 and |16communicate with a float chamber |13 in which the oil and water are insurface contact at a levelcorresponding to the level |10. A properlybalanced float |19 is disposed in the chamber |18, being so formed as tooat in water and sink in oil. The position of this oat will thus changein response to changes in the level |10. This float may be pivoted on apin |80 connected to an arm I 8| which is connected to a valve |82 inthe pipe |11 by any suitable means such as a link |83 connected to anarm |84 of the valve |82 pivoted at |85 and operatively connected to thestem |86 of this valve. If the water level rises, the valve |82 willthus be opened a further distance to drain additional quantities ofwater from the tank ||5 and thus maintain the water level constant.Various other systems for controlling the position of this water levelmay be utilized without departing from the spirit of the presentinvention.

I have found that in some instances there is a tendency for the settlingcoalesced water masses to carry downward therewith particles of oil.This is not conducive to a clean separation, and, if allowed tocontinue, will result in contaminated water bleeds, the oil beingcarried downward into v the body of water in the bottom of the tank. Ifthis action takes place and is detrimental, it can be corrected bymoving masses of water upward through the body of water to sweep out anyoil present and prevent downward movement of oil toward the waterdraw-off pipe |11.

A system wh'ich I have found very satisfactory in this regard isillustrated in Figs. 3 and 6. Disposed above and in protectingrelationship with the water draw-olf pipe |11, I illustrate amultiorifice discharge head |90. This head may be formed of a cap |92,best shown in Fig. 6, and provided with a plurality of orifices |93formed to direct water upward and outward. Certain o1' these orificesmay be vertically disposed, though best results are obtained if otherorifices are angularly disposed relative to the horizontal. A plate |95closes the cap |92 and receives a pipe |96 to which water is deliveredby a pipe |91. The incoming water is thus sprayed into the body of waterin the lower end of the tank ||5 to form water masses which slowly risetoward the surface |10 due to the inclined nature of the orices or tothermal action or to a diierence in density if the incoming water isfresh, or t0 various combinations of these factors. A desirable thermaleifect is obtained by delivering to the pipe |91 water which is slightlyhotter than the water inthe bottom of the tank ||5. This may beaccomplished by connecting the pipe |91 to the pipe 16, and thus to thedischarge of the pump 83, the flow being controlled by a valve |99.

The action of these rising water masses is to sweep from the body ofwater in the bottom of the tank ||5 any oil or reverse-phase emulsion.The upward movement of the newly added water particles moves such areverse-phase emulsion toward the surface 10 and thence into theauxiliary electric eld |1| in which such an emulsion is separated.'I'his expedient of introducing Water masses into the body of water inan electric treater is particularly valuable when treating certain oils,and permits larger quantities of Water to be added to the incoming oilin the performance of the process herein disclosed in detail.

In some instances it is possible to accelerate the separation of theparticles of oil in such a mass of Water by adding to the Water flowingthrough the pipe |91 a small quantity of a chemical deemulsifying agent.Various types of such agents are known. Particularly desirable resultshave been obtained by the use of a chemical de-emulsifying agent whichis both oil soluble and water soluble though other rchemicalde-emulsifying agents can be used.

The treated oil moves from the upper end of the tank ||5 through a pipe200, the flow being controlled by a valve 20| which in turn assists incontrolling the pressure in the tank ||5. I'his treated oil may be moveddirectly into the rening system, though I find it preferable todischarge same into a treated-oil storage tank 202 where some additionalseparation of the water will take place.

A pump 203 is shown for withdrawing the treated oil from the tank 202and moving same through a pipe 204 to the heat exchanger 53. Additionalheat is supplied at this point and the treated oil moves through a pipe205 to the heat exchanger 53. Being thus additionally heated, thetreated oil moves through the pipe 6| to the still 2|. Here certainlighter vfractions are removed, as previously described, the topped oilmoving through a pipe 201 to the still 3|. This sequence is continued toremove successive fractions, and, in the embodiment shown, the heavierconstituents of the oil finally move from the still 5| through a pipe208 to a cracker 2|0. Various of such crackers are known in the art andneed not be speciiically described. Usually, however, these crackersinclude a plurality of tubes which are externally heated and whichconduct the heavier constituents of the oil. The heat supplied in thecracker 2|0 causesl cracking and vaporization, 'the vapors movingthrough a, pipe 2|| and being condensed in a condenser 2|2, the residuebeing discharged from the cracker 2| 0 through a pipe 2|5.

By way of example, and without limiting myself thereto, operatingconditions and results with a typical oil will be given. The oil in thisexample contained only from .4% to .5% of water, but still containedfrom 100 to 250 grams of water-:dissolved salts per barrel, these saltsbeing predominately magnesium chloride and calcium chloride. By use ofthis process, it was found possible to consistently lower the saltcontent to 10 grams per barrel or less, and in some instances to 5 gramsper barrel. This oil was treated at a rate of 2250 barrels per day pertreater, and the average water content of the treated oil was in thisinstance reduced to ,2%.

In this example, the incoming oil moved through the heat exchangers 23and 33 and was raised to a temperature from to 150 F. 'Ihe water used inthis example was withdrawn from several of the condensers 24, 34, 44 and54, an expedient which can be utilized if desired, and was at atemperature of about 120 F., this temperature being increased in theheater 19 to a value of about 160 F., a temperature which, in thisexample,- was somewhat above the temperature of the oil in the pipe 15.The introduction of this water into the pipe 15 thus served toadditionally heat the oil, and the temperature of the preliminarymixture entering the emulsifying means was approximately F.

In this example, the available water supply was fresh water whichincidentally contained various salts in very small quantities. This wasa typical water such as is used for drinking purposes and such as can beobtained from lak-es, rivers, domestic water supplies, etc. Percentagesof water between 10% and 50% could be used with success, thoughapproximately 20% of water gave 2,182,145 `best results in forming theresulting mixture.

Operation was slightly improved by jetting additional water upward inthe body of water in the tank H5, the water thus introduced being at atemperature slightly higher than that of the water in the tank. However,the system operated entirely successfully without the addition of waterat this point, though it was found that clearer water bleeds could beobtained by such injection.

'I'he degree of mixing was so controlled as to produce a relativelyunstable mixture or emulsion in which a major portion of the .originalwater droplets coexisted with the droplets of the water at the time ofintroduction into the electric field. In this example, the mixture wasnot relatively stable, and substantially 90% of the water wouldgravitationally separate from the oil as free or emulsifled water if themixture was allowed to stand quiescent for two or three days at itstemperature of about 150 F. It was found that this type of emulsioncould be produced by properly controlling one or more of the emulsifyingmeans above-mentioned, but the best results were obtained when using avalve, such as shown in Fig. 2, in conjunction with the emulsifyingdistributor means |05.

It was found desirable in this example to carry a slight pressure in theelectric treater 81. A pressure of 20 lbs/sq. in, gave very satisfactoryresults. The pressure drop across the emulsifying distributor means |05was approximately 12 lbs/sq. in., and the pressure drop across theemulsifying valve, such as shown in Fig. 2, was approximately 10lbs./sq. in. Additional drops in pressure due to pipe friction broughtthe pressure in the pipe 15 to approximately 50 lbs/sq. in.

The voltages mentioned above were used, and the water content of thetreated oil was approximately .2%. Microscopic examination of the oildischarged from the upper end of the treater 81 showed the presence ofminute water droplets of a size in the neighborhood of one mu,approximately the size of the original droplets present in the incomingoil. The oil withdrawn from the electric treater contained substantially-none of the original water droplets present in the incoming oil, thosewater droplets present in the treated oil being predominantly dropletsof the added water. On the other hand, the water drawn from the treaterwas of a composite composition, containing the salts present both in theoriginal water droplets and in the added water.

Prior to installation of the invention in this exemplary refinery, itwas customary to treat this oil with large quantities of ammonia. Byprocessing the oil as herein-disclosed before fractional distillationthereof, it was found possible to effect a saving of approximately$300.00 per month in the amount of ammonia utilized. In addition, if therefinery equipment was utilized on oil not treated by the processherein-described. it was found that even ii considerable quantities ofammonia. were utilized, the equipment could operate for only limitedperiods without clogging. For instance, it was necessary to clean thecracker every six or ten days and the stills every fifteen or twentydays. When processing th'e oil by the method herein-disclosed, it wasfound that the subsequent equipment could be operated continuously forthirty-five days or more before clogging of the cracker or otherequipment took place to any detrimental extent. In addition, corrosiondiillculties were minimized and better products produced. Asillustrative of the latter factor, this refinery was unable to produceasphalt of the desired solubility prior to use of the present invention.Thereafter, the solubility of the asphalt was raised to 99.9%.

In general, it will be found that the process '5 operates best ifvarious factors are controlled to bring them within the followingconcepts. It will be clear, however, that the following statements areto be applied to ranges, conditions or values which give best results,and that these will 10 varywith different oils, and that,` in someinstances, they do not represent fixed limits but can be departed fromin some degree if optimum results are not necessary. The followingsuggested values apply particularly to an oil containing water in whichthe impurities are dissolved:

As to the added water, various waters can be used, so long as this wateris of different composition from that of the original water droplets,within the meaning of this term as hereinbeforedened. Based on thevolume of the oil, various percentages can be used. The lower limitappears to be about 8%, and the upper limit appears to be determinedonly by the tendency to form inverse-phase emulsions in such amount asnot to be readily treatable by the electric field. In

v some instances, 50% or somewhat more can be utilized. At the higherpercentages, it is preferable to use the water spray in the bottom ofthe treater. With most oil, optimum results have been obtained between15% and 25%, approximately 20% appearing to give the best results. Thetemperature of the water at the time it is introduced into the oil isnot particularly critical and depends in part upon the temperature ofthe oil. In some instances, water can be introduced at room temperature,though better results have been obtained by use of water. at elevatedtemperatures. The usual temperature range is from 100 F. to 210 F. buthigher temperatures can be used, up tothe boiling point at the pressureutilized.

As to the incoming oil, various oils can be successfully treated, solong as they do not shortcircuit the electrodes. The water presenttherein will be dispersed in the form of relatively small droplets,though the process is not limited by the exact size of these originaldroplets. It is particularly effective on oils in which these originalwater droplets cannot be separated conveniently or economically. It isnot always necessary to heat the oil before injection of the addedwater, though heat usually improves the process. The temperature is notcritical, and excellent results have been obtained with oils from 100 F.to 225 As to the resulting mixture or emulsion, the fundamental conceptis to disperse droplets of the added water in the oil to coexist withthe original water droplets. This can be done in various ways, and if asupplementary mixing action is used, it is very desirable that themixing action should not be of such character as to itself cause a majorportion of the original droplets to combine with the added water. Themost desirable mixture is one in which a major portion of the originalwater droplets coexist with droplets of the added water until such timeas it is subjected to the action of the electric field. Best resultshave been obtained from a resulting mixture in which the average size ofthe added water droplets is larger than the average size of the originalwater droplets. In addition. it is ofter. desirable to instances oncertain oils without additional emulsifying means, or such a pump can beused in conjunction with the mixing action resulting from injection, orfrom the use of an emulsifying distributor means, or from both.

In other instances, an emulsifying valve, properly designed and properlycontrolled can be used, or this can be used in conjunctionwith any ofthe additional. emulsifying means above-mentioned. In some instances,particularly desirable Aresults have been obtained by dividing thestream of the preliminary mixture, moving a portion through a suitableemulsier and another portion in by-passing relation with this emulsier.The two streams join beyond the emulsifier and in so joining, anadditional gentle mixing action is vobtained which rather uniformlydistributes the droplets of the by-passed stream throughout the mixturewhich moves from the emulsier.

As a general rule, the desirable type of resulting mixture or emulsionrequires a definitely limited mixing action. Intimate mixing, such aswould result in homogenization, should be avoided. A centrifugal pumpmay be designed and operated to produce an emulsion departing from thedesired character and is usually not the best type of emulsifying deviceto use, except that it will work successfully on certain selected oilsif properly designed and controlled so as not too intimately to mix theoil and the added water. If a valve, such as shown in Fig. 2, is used asthe emulsifying means, the desirable pressure drop thereacross willdepend upon the oil being treated and upon the other emulsifying actionsused, if any. In using such a valve with the water injection systemshown and with the emulsifying `distributor means, a pressure dropthereacross from 3 lbs/sq. in. to 60 lbs/sq. in. has been used withsuccess, though these limits can often be departed from.' From 5 lbs/sq.in. to 15 lbs/sq. in. is usually best in this regard.

In some instances, the mixture may desirably `be heated with or withoutheating the incoming oil or the water. Best temperatures of theresulting mixture when subjected to the eld are from F. to 190 F. thoughatmospheric tem- Deratures are sometimes effective.

As to the electric treater 81, any electric treater capable of bringingthe coexisting droplets together can be used, such action being hereintermed coalescence. Alternating current fields are preferred, eitherconstantly occurring or intermittently applied, though such coalescencecan take place in a uni-directional field of constant or pulsatingpotential. Fields resulting from the application of short electricsurges to the electrodes, or application of peaked potentials to theelectrodes, can also be used with success. Relatively high potentialsare preferred. the potentials and type of current being commensuratewith those used in the art of electrically dehydrating emulsions. Inaddition, various electrode structures can be used with varying degreesof heavier oils, or with mixtures having no distinct sludging tendency,it is sometimes possible to introduce the emulsion into the tank H5 at apoint spaced from the main field, allowing the emulsion to subsequentlygravtate or otherwise move thereinto. With such oils, introduction intothe auxiliary treating space I 1| can sometimes be used. Whilesatisfactory results can sometimes be obtained by maintainingsubstantially atmospheric pressure in the treater 81, better resultshave been obtained by maintaining therein a pressure of from 5 to 25lbs./sq. in.

As to the treated oil moving from the upper end of the electric treater81, the water content thereof may be slightly above or slightly belowthe water content of the incoming oil. Usually, the process will producea treated oil containing about the same amount of water as was presentin the incoming oil. The composition of this water in the treated oilwill depend largely upon the composition of the added water. In view ofthe fact that the process acts in eiect to replace droplets of theoriginal water with droplets of the added Water, it Will be clear thatthe salt content of the outowing oil is largely within the control ofthe operator. If it should be desired to even increase the total saltcontent, by replacing deleterious salts with other salts having nodetrimental action on the subsequent equipment. this can be readilyaccomplished. On the other hand, it is possible to remove a largeportion of the salts in the original water droplets, and subsequentlyre-run the treated oil through the system, adding salt water, andproduce a salty oil, thus indicating that the replacement actionmentioned above is reversible.

Temporary storage of the treated oil in tank 202 `is not essential,though it will be found that some additional separation of water willtake place therein, and this expedient is often desirable in refinerypractice.

Coming now to the general problemk of removing impurities associatedwith the oil, as distinct from being associated with any Water dropletswhich may be present, such impurities may be dissolved in, or dispersedin, the oil. Various acids dissolved in the oil and various impuritiescolloidally'dispersed in the oil, for instance mud and sand, are typicalexamples. Assuming that the incoming oil contains not. more than a fewper cent of water, and that this water carries various`impurities whichwill be removed as above set forth, it will be clear that acids thusdissolved other impurities, such as salts, etc. Assuming that thisincoming oil also contains acid dissolved in the oil and mud colloidallydispersed therein, it has been found that the process will removesubstantial amounts of these impurities by'following the procedureoutlined above. Just why this is the case is not distinctly understood.It has been .definitely ascertained that neither oil-dissolved acid northe colloidally-dispersed mud will combine with the added water to anymajor degree during the mixing action herein contemplated, for, if thewater is .separated from the resulting mixture before subjection to theelectric eld, it will be found that most of these impurities remain inthe oil and have not been transferred to the water. However, when theresulting mixture is subjected to the action of an electric eld, thedissolved acid and colloidallydispersed mud are transferred in largemeasure from the oil to the water,E and appear in the water separated inthe electric treater.

So also the invention is applicable to removal of impurities dissolvedin, or dispersed in, the oil, regardless of whether or not waterdroplets are present. For instance, it has been found possible to removeoil-dissolved acid and colloidallydispersed impurities from an oil whichis substantially dry. In this instance, water is added in about the sameproportions as mentioned above. One or more mixing steps, asabove-defined, can be utilized, though in general it can be stated thata somewhat more violent mixing action can be utilized in thisconnection, so long as the resulting mixture is readily treatable by anelectric eld to coalesce the droplets of the added water presenttherein. Here again it has been found that the oil-dissolved acid andthe colloidally-dispersed impurities become associated with the addedwater by some action in the electric field, and not in the mixing stepitself. Acids, or other impurities dissolved in, or dispersed in, an oilcan thus be removed by the process..

The invention is not limited to treatment' of an oil preparatory toadditional refining by fractional methods. Various other uses of theinvention will be apparent to those skilled in the art. If used with arefinery system, the connections disclosed will be found of particularutility in saving heat, utilizing the water from the condenser means,and being desirable in other connections. However, the invention isapplicable to various types of refining units, and need not be connectedthereto in heat-transferring relationship if this is not desired.

While the process has been particularly defined with reference to adehydrated oil, it is applicable to removing impurities from variousoils under the principles outlined above, regardless of whether theyhave been previously treated in one way or another, and regardless ofwhether they are to be additionally treated by fractionation. Nor is italways essential that the oil be of lower gravity than the addedwater.If the converse is true, the principles herein-disclosed can be appliedby withdrawing water from the upper end of the treater tank, and thehydrocarbon from the lower end, suitable changes in position of theinsulators being made to prevent short-circuiting of the electrodes.Such conditions may be met in treating certain tars to remove impuritiestherefrom.

The term relatively fresh water, as used in the claims has reference, ifthe oil carries dispersed impurity-containing water, to a water which ifit contains any of the impurities to be removed has a materially lessconcentration thereof than does the dispersed water, or, if the oilcarries no dispersed impurity-containing water the term has reference toa water which has no more than a small concentration of the impuritiesto be removed.

In general, the present process comprises the treatment of a .mineraloil containing no more than a few per cent of water by mixing arelatively fresh water therewith preparatory to electric treatment. Thecharacter of mixing is important and, as previously pointed out, must belimited to a value at which the desired action will be obtained. Thismixing should be of such character as to disperse the relatively freshwater eiectively throughout the oil and to form an emulsion which is ina condition to be continuously and substantially completely resolvablewith the aid of an electric field into oil and water, without theaccumulation of such amount of sludge comprising unresolved emulsion aswould interfere with the maintenance of the electric eld. Any suchincreasing accumulation of sludge would seriously interfere with thecontinuity of the process, which, being often connected to reneryequipment, must remain on-stream for long periods of time. In addition,electric treatment well suited to the artificial emulsion or mixtureshould be used, and should be capable of continuously treating same sothat substantially complete resolution can be obtained by subjection toan electric field and separation of the coalesced water masses.

Various other changes and modifications can be made without departingfrom the spirit of the present invention as defined in the appendedclaims.

This application is a continuation in part of my application Serial No.66,404, filed February 29, 1936, entitled Improved process and apparatusfor treating oil.

I claim as'my invention:

1. A process for treating a mineral oil contain'- ing no more than a fewpercent of water to remove impurities dissolved or dispersed in the oilphase or the water phase, which process includes the steps of mixingsaid mineral oil and a relatively fresh water, said mixing being of sucha character as to form a mixture of the relatively fresh water and oilbut insuiiicient to cause a'predominant portion of the impurities tobecome associated with said relatively fresh water; suhjecting themixture to the action of an electric eld to coalesce the water and causeimpurities to become associated therewith; and separatingthe coalescedwater containing impurities from .the oil.

2. A process for treating .a mineral oil contain- 4 ing no more than afew percent of water to remove impurities dissolved or dispersed in theoil phase or in the water phase, which process includes the steps of:mixing said mineral oil and a relatively fresh water to disperse therelatively fresh water effectively throughout the oil, said mixing beingof such character as to form an emulsion which is in a condition to becontinuously and substantially completely resolvable with the aid of anelectric eld into oil and water without the accumulation --of suchamount of sludge comprising unresolved emulsion as would interfere withthe maintenance of the electric field; and substantially completelyresolving said emulsion by subjecting a continuous stream of saidemulsion to the action of an electric field to coalesce the dispersedwater and separating the coalesced water masses from the oil, wherebysaid process may be maintained in continuous operation for extendedperiods of time.

3. A process for purifying a mineral oil refinery charging stockcontaining no more than a few percent of water to remove impuritiesdissolved or dispersed in the oil phase or in the water phase and whichupon heating in the refinery equipment vwill detrimentally affect thisequipment or the mixing being of such character as to form an emulsion.which is in a condition to be continuously and substantially completelyresolvable with the aid of an electric field into oil and water withoutthe accumula-tion of such amount of sludge comprising unresolvedemulsion as would interfere with the maintenance of the electric field;and substantially completely resolving said emulsion by subjecting acontinuous stream of said `emulsion to the action of an electric fieldto coalesce the dispersed water and separating the coalesced watermasses from the oil to such extent as to leave no more than a fewpercent of water remaining in the oil comprising the purifled refinerycharging stock, whereby said process may be maintained in continuousoperation for extended periods of time.

4. A process for purifying a mineral oil refinery charging stockcontaining no more than a few percent of water to remove impuritiesdissolved or dispersed in the oil phase or in the water phase and whichupon heating in the refinery equipment will detrimentally affect thisequipment or the -products produced, said impurities comprising salinematerial, which process includes the steps of mixing with a stream ofsaid refinery charging stock a relatively fresh water to disperse therelatively fresh water effectively throughout the oil, said mixing beingof such character as to form an emulsion which is in a condition to becontinuously and substantially completely resolvable with the aid of anelectric field into oil and Water without the accumulation of suchamount of sludge comprising unresolved emulsion as would interfere withthe maintenance of the electric field and which emulsion containsdroplets of said relatively fresh water coexisting with said salinematerial; and substantially completely resolvingsaid emulsion bysubjecting a continuous stream of said emulsion vto the action of anelectric field to coalesce the dispersed water and separating thecoalesced Water masses from the oil to such extent as to leave no morethan a few percent of Water remaining in the oil comprising the purifiedrefinery charging stock, whereby said process may be maintained incontinuous operation for extended periods of time.

5. A process for treating a mineral oil containing no more than a fewpercent of water to remove saline material dispersed in said mineraloil, which process includes the steps of: mixing said mineral oil and arelatively fresh water, said mixing being of such a character as to forma ymixture of the relatively fresh water and oil but insufcient tocausea predominant portion of the saline material to become associated withsaid relatively fresh Water; subjecting the mixture to the action of anelectric field to bring the saline material and the water together andto coalesce water; and separating the coalesced water from the oil.

6. A process for treating a mineral oil containing no more than a fewpercent of water to remove saline material dispersed in said mineraloil, which process includes the steps of: mixing said mineral oil and arelatively fresh water to disperse the relatively fresh watereffectively throughout the oil, said mixing being of such character asto form an emulsion which is in a condition to be continuously andsubstantially completely resolvable with the aid of an electric fieldinto oil and water without the accumulation of such amount of sludgecomprising unresolved emulsion as would interfere with the maintenanceof the electric field; and. substantially completely resolving saidemulsion by sub- 'continuous operation for extended periods of time.

7. A process as defined in claim 3 including the step of heating the oilfrom which said coalesced masses have been separated to a temperaturesufficient to remove vapors therefrom.

8. A process as defined in claim 5 including the step of producing saidmineral oil containing no more than a few percent of water by treating acrude oil emulsion to coalesce and separate therefrom dispersed brine toproduce an oil containing dispersed saline material, but containing nomore than a few percent of water.y

9. A process as defined in claim 1 in which said coalesced Water isseparated to such an extent as to leave no more than a few percent ofwater in the oil.

10. A process as defined in claim 2 in which said mixing is effected atleast in part by bringing together at superatmospheric pressure streamsrespectively comprising said mineral oil and said relatively freshWater, said superatmospheric pressure being sufficient to move theresulting stream into said electric field.

ll. A process as defined in claim l in which said coalesced water isseparated from the oil in a separating zone from which the water and oilare separately withdrawn, and including the step of bringing together atsuperatmospheric pressure streams respectively comprising said mineraloil and said relatively fresh water, said superatmospheric pressurebeing sufficient to move the resulting stream into said electric fieldand maintain a superatmospheric pressure in said separating zone.

12. A process as defined in claim 2 in which said mixing is performed atleast in part by bringing together and blending streams respectivelycomprising said oil and an oil containing droplets of said relativelyfresh water dispersed therein to disperse the droplets of relativelyfresh water throughout the resulting stream.

13. A process as dened in claim 2 in which said mixing comprisespreliminarily mixing the mineral oil and the relatively fresh water,dividing the preliminarily mixed constituents into two portions,additionally mixing each portion while mixing one portion in such manneras to disperse the relatively fresh water into droplets of an averagesize smaller than those resulting from the additional mixing of theother portion, and blending the two portions together to form adispersion containing interspersed droplets of the relatively freshwater derived from both portions.

14. A process as defined in claim 2 in which the mixing of the mineraloil and the relatively fresh water is performed in successive mixingsteps.

15. A process as defined in claim 2 in which at least a part of themixing is performed adjacent the point of discharge into said electricfield. l 2

16. A process as defined in claim 2 in which said electric field isestablished in an oil environment of sufficient resistivity to permitmaintenance of the field at coalescing potential when treating saidemulsion, this emulsion being continuously introduced into this oilenvironment for treatment by said electric iield.

17. A process as defined in claim 2 in which said electric eld isestablished in an oil environment of a separating zone containingelectrically-treated constituents undergoing gravitational separation,the lower end of said zone containing a body of water, and in which anauxiliary electric field is established at a position between saidfirst-named field and saidv body of Water to treat electrically thewater masses moving downward to said body of water.

18. A process as dened in claim 1 in which said impurities comprisesalts dissolved in water droplets dispersed in the oil in amount notmore than a few percent whereby said oil con-v tains dispersed brine,and in which said relatively fresh water contains some of the same saltsas are present in said brine but in a concentration substantially lowerthan the concentration thereof in said brine.

19. A process for treating a mineral oil to remove therefrom impuritiescarried by small water droplets dispersed in the oil, said oilcontaining no more than a few percent of water, which process includesthe steps of: mixing said mineral oil and a relatively fresh water, saidmixing being of such character as to form a mixture of the relativelyfresh water and oil but insufficient to cause a predominant portion ofthe impurities carried by the water droplets of the oil to becomeassociated with said relatively fresh water and said mixing being ofsuch character as to disperse the relatively fresh water into the oil indroplets of heterogeneous particle size and of an average size largerthan the water droplets in the mineral oil to be treated; subjecting themixture to the action of an electric field to coalesce the droplets ofrelatively fresh water with the droplets carrying said impurities thuscausing the impurities to become associated with the coalesced water;and separating the coalesced water containing impurities from the oil.

20. A process for treating a mineral oil to remove therefrom impuritiescarried by small water droplets dispersed in the oil, said oilcontaining no more than a few percent of water, which process includesthe steps of: mixing said mineral oil and a relatively fresh water todisperse the relatively fresh water effectively throughout the oil, saidmixing being of such character as to form an emulsion which is in acondition to be continuously and substantially completely resolvablewith the aid of an electric eld into oil and water without theaccumulation of such amount of sludge comprising unresolved emulsion aswould interfere with the maintenance of the electric eld; andsubstantially completely resolving said emulsion by subjecting acontinuous stream of said emulsion to the actionv of an electric eld tocoalesce the dispersed water and separating the coalesced water massesfrom the oil, whereby said process may be maintained in continuousoperation for extended periods of time, said mixing and separatingcstepsbeing of such character that some of the droplets of relativelyfreshwaterin said emulsion are of such size as to remain in small amount inthe oil following separation of said coalesced masses therefrom.

HAROLD C. EDDY.

